A machine such as a mechanical press, shear, or stamper that is used for high-energy metal cutting and/or shaping operations is described in German 2,924,834 of Zimmermann. Here the normally continuously rotating input element is connected to the rotary but only intermittently rotated output element by a pair of clutches, with a pair of brakes connected to the elements also. The two clutches are hydraulically independently actuatable. The redundancy of the clutches and brakes ensures that the system can be made to operate at least partially, or at least can be shut down, if one of the brakes or clutches fails. Thus the two clutches and the two brakes are substantially identical.
A press described in U.S. Pat. No. 6,142,275 of Kreisl has a nonrotating tube shaft centered on an axis, a rotatable output shaft coaxially received in the tube shaft and having a shaft end, and a supply of fluid under pressure. A brake element fixed on the tube shaft forms with an axially movable brake element angularly coupled with the output shaft a pressurizable brake chamber. A fluid line extending from the brake chamber through the tube shaft to the fluid supply can pressurize the brake chamber and thereby couple the brake elements with each other so that the output shaft is braked against the tube shaft. A flywheel rotatable about the axis on the tube shaft carries a first clutch element rotatable about the axis. A second clutch element rotatable about the axis adjacent the first clutch element forms therewith a pressurizable clutch chamber. Another fluid line extending from the clutch chamber to the fluid supply can pressurize the clutch chamber and thereby couple the clutch elements with each other so that the output shaft is coupled to the flywheel.
The problem with the coupling between a drive motor and a press, shear, or stamper is that it is normally designed as a compromise between the high slippage encountered at relatively low torque as the output element is brought up to speed and the low slippage encountered at relatively high torque during the actual metal deforming or cutting operation. It is necessary for the coupling to dissipate considerable heat during the startup phase during which only a relatively modest amount of torque is transmitted from the input element to the output element, while during the actual working phase that follows there is little slippage, so little heat is generated, while considerable torque is transmitted through the coupling.